Some opaque data types require special processing when they are deleted. For example, if an opaque type contains spatial or multi-representational data, it might provide a choice of how to store the data: inside the internal structure or, for large objects, in a smart large object.
The database server removes opaque types by calling a user-defined support function called destroy( ). When you execute the DROP TABLE statement on a table whose rows contain an opaque type, the database server automatically invokes the destroy( ) function for the type. The destroy( ) function can perform certain operations on columns of the opaque data type before the table is dropped. For more information about the destroy( ) support function, see IBM Informix User-Defined Routines and Data Types Developer's Guide.
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